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Kwila

Scientific name

Intsia bijuga (formerly Afzelia bijuga syn. Afzelia australis), I. palembanica. Family: Leguminosae

Other names

Johnstone River teak; Scrub mahogany (North Queensland); Merbau (Malaysia); Vesi (Fiji); Moluccan ironwood (United Kingdom); Go-nux (Vietnam); Ipil (Philippines); Hintzy (Madagascar); Melila, Bendora (Papua New Guinea); Lumpho, Lum-paw, makamong (Thailand); Kivoli, Vuvula (Solomon Islands)

Description

  • Large hardwood tree
  • Grows to 40m high
  • Trunk is 0.6m diameter
  • Often a bushy tree forming a spreading canopy

Occurrence

  • Johnstone River and Daintree areas of North Queensland
  • Malaysia
  • Fiji
  • Vietnam
  • Philippines
  • Madagascar
  • Papua New Guinea
  • Thailand
  • Solomon Islands
  • New Caledonia
  • Vanuatu
  • Samoa

Appearance

Colour

  • Heartwood yellowish-brown or orange-brown when first cut, turning darker with age to brown or deep reddish-brown
  • Sapwood white, pale yellow or buff and sharply distinct from heartwood

Grain

  • Grain varies but usually interlocked or wavy.
  • Texture is coarse but even.
  • Attractive figure (pattern) on back-sawn material.

Uses

Engineering

  • Cross arms
  • Bridge building
  • Piles
  • Sleepers
  • Posts
  • Wharfing
  • Mining timbers

Construction

  • Framing
  • Decking
  • Treads
  • General construction

Decorative

  • Quality furniture, outdoor furniture
  • Turnery, parquetry

Others

  • Boat building (especially for decking)
  • Vats
  • Musical instruments
  • Tool handles

Properties

  • Density: 830kg/m3 at 12% moisture content; about 1.2m3 of seasoned sawn timber per tonne.
  • Strength groups: S2 unseasoned, SD3 seasoned.
  • Stress grades: F11, F14, F17, F22 (unseasoned), F14, F17, F22, F27 (seasoned) when visually stress-graded according to AS 2082—2000: Timber—Hardwood—Visually stress-graded for structural purposes.
  • Joint groups: J3 unseasoned; JD2 seasoned.
  • Shrinkage to 12% MC: 2.6% (tangential), 1.2% (radial).
  • Unit shrinkage: 0.30 % (tangential) 0.19 % (radial)—these values apply to timber reconditioned after seasoning.
  • Durability above-ground: Class 1 (life expectancy more than 40 years).
  • Durability in-ground: Class 3 (life expectancy 5–15 years).
  • Lyctine susceptibility: untreated sapwood susceptible to lyctid borer attack.
  • Termite resistance: resistant.
  • Preservation: sapwood readily impregnates with preservative.
  • Seasoning: seasons well with kiln or air-drying, with little degrade and very little shrinkage or movement.
  • Hardness: hard (rated 2 on a 6-class scale) to indent and work with hand tools.
  • Machining: working properties vary; cuts cleanly but may blunt or gum cutting edges; cutting angle should be reduced to 20° when planing quarter-sawn stock; turns well.
  • Fixing: can split unless pre-bored, but holds fastenings well.
  • Gluing: glues satisfactorily except with casein glues.
  • Finishing: paints, stains and polishes well, but gum bleed-through or oily patches may affect the finish.

Identification features

General characteristics

  • Sapwood: sharply distinct from the heartwood
  • Heartwood: dark red-brown or yellow-brown
  • Texture: coarse and even; grain often interlocked

Wood structure

  • Vessels: moderately large, visible to naked eye; short radial pairs or multiples and solitary cells; often visible sulphur yellow and dark-coloured deposits; vessel lines prominent on longitudinal surfaces

Research and resources

  • Boland, DJ, Brooker, MIH, Chippendale, GM, Hall, N, Hyland, BPM, Johnston, RD, Kleinig, DA and Turner, JD 2006, Forest trees of Australia, 5th ed., CSIRO Publishing, Collingwood, Australia.
  • Bootle, K 2005, Wood in Australia: Types, properties and uses, 2nd ed., McGraw-Hill, Sydney.
  • Ilic, J 1991, CSIRO atlas of hardwoods, Crawford House Press, Bathurst, Australia.
  • Queensland Government, DAF 2018, Construction timbers in Queensland: properties and specifications for satisfactory performance of construction timbers in Queensland. Class 1 and Class 10 buildings, Books 1 & 2, Department of Agriculture and Fisheries, Brisbane.
  • Standards Australia, 2000, AS 2082—2000: Timber—Hardwood—Visually stress-graded for structural purposes, Standards Australia International, Strathfield, NSW.